Petaluma rebuilding Sonoma Mountain Parkway

When Sonoma Mountain Parkway was first built in 1991 to accommodate Petaluma’s northeast expansion, the city used as a base layer rocks hewn from the Zamaroni quarry in Santa Rosa.

It proved to be a solid road building material, except during the rain, which it is wont to do in Petaluma each winter. The rain caused the base layer to erode, creating a series of manhole-sized craters and cracks that have required frequent attention and left the asphalt looking like a patchwork quilt.

“We thought the base would be great, but it doesn’t do well when it gets wet,” said Jeff Stutsman, a senior civil engineer for the city. “It was a base failure.”

After years of cosmetic improvements, the city is addressing the structural problems on Sonoma Mountain Parkway, launching a project to redo the road from the bottom up. The two month project, which began in earnest last week, will leave a smoother driving surface for east side motorists. The $1.7 million construction is paid for by state gas tax revenue.

“I think we had to redo the road, it had become so deteriorated,” said Kathy Miller, a city councilwoman and the city’s Sonoma County Transportation Authority representative. “All the Band-Aids that we used on it in the past are no longer sufficient to keep it usable.”

Instead of a typical repave, the city is using a process on the parkway known as full depth reclamation, Stutsman said. The top five inches of asphalt have been scraped off the road and stored in a heap at the Petaluma Municipal Airport for later use. Next, the base layer will be ground up and mixed with cement to make a sturdier foundation.

The recycled asphalt will then be trucked back in from the airport, and finally the street will get topped off with a hot layer of new asphalt to seal it.

The new road is expected to have a 20-year lifespan, Stutsman said.

“Instead of fixing the potholes, we’re fixing the base,” he said.

This spring, crews began adding curb cuts and wheelchair ramps. On June 3, workers brought out the heavy machinery, shifting traffic in order to pave the south lanes. On July 5, traffic is scheduled to shift again so crews can rebuild the north lanes. The project is set to wrap up on Aug. 9.

The project is between Corona Road and Campus Circle Drive at the SRJC entrance, as well as between Wyndham Way and East Washington Street.

During construction Liverpool Way will be permanently closed and detours will be set up to use Wellington Place. Campus Circle North will be closed permanently and detours at SRJC will be set up to utilize Campus Circle South. Riesling Road south of Sonoma Mountain Parkway will be permanently closed and detours set up back to Sonoma Mountain Parkway or Maria Drive. The driveway into and out of Leghorn Market Place will be closed and detours set up to Riesling or other side streets.

Miller said the city chose to do the work in the summer when school is out and the weather is more favorable for road work.

“We’ve been getting remarkably few complaints, which makes me super happy,” Miller said. “Everyone has told me how happy they are we’re working on it.”

The city approved the project in April with funding from SB1, the state gas tax adopted in 2017 that voters affirmed in the 2018 election.

The city is already planning for another major road reclamation project next summer, a rebuild of Maria Drive, which ails from the same base failure issue as Sonoma Mountain Parkway.

“We’re looking to do Maria Drive as our next big project,” Miller said. “It’s a mess.”

(Contact Matt Brown at matt.brown@arguscourier.com.)